This laboratory is engaged in studies relating to the stimulation of cyclic AMP content in thyroid cells in monolayer culture. This system has been found to be very sensitive in that stimulation is observed at physiological concentrations of thyrotropin (TSH). Studies are ongoing to compare the bioactivity of TSH present in the serum of patients with hypothyroidism with the TSH content in the same sample as determined by radioimmunoassay. This requires the partial purification of TSH by gel filtration. Studies are also underway to examine the nature of the stimulatory effect of human lymphocytes on cultured thyroid cells, as a means of investigating the pathogenetic mechanism of Graves' disease. BIBLIOGRAPHIC REFERENCES: O.H. Clark, W.R. Lambert, R.R. Cavalieri, B. Rapoport, M.E. Hammond, and S.H. Ingbar: Effect of iodide on compensatory goiter in rats following hemithyroidectomy. Surg. Forum, 26:182, 1976. B. Rapoport, M.N. West, and S.H. Ingbar: On the mechanism of inhibition by iodine of the thyroidadenylate cyclase response to TSH. Endocrinology, 99:11, 1976.